This invention relates to elements for use in inductive couplers for downhole components. U.S. Pat. No. 6,670,880, which is herein incorporated by reference, discloses a downhole transmission system through a string of downhole components. A first transmission element is located in the one end of each downhole component, which includes a first magnetically conducting, electrically-insulating trough, and a first electrically conductive coil lying there in. A second data transmission element is located in the other end, with a similar arrangement comprising a second magnetically conducting, electrically insulating trough and a second electrically conductive coil. The transmission system further comprises an electrical conductor in electrical communication with and running between each first and second coil in the downhole component. The string of downhole components is cooperatively arranged such that the troughs are in magnetic communication with each other and transmit signals through induction.